Exposure-related FEV1 declines worse in firefighters who also smoked

Action Points

Thirteen years after 9/11, lung function declines related to toxic dust exposure persisted among World Trade Center first responders, with smokers and those with the greatest exposures having the largest pulmonary declines.

Note that the study suggests that the combined effects of the pulverized building materials and the chemical by-products of combustion contained in the World Trade Center dust are significantly more toxic to the respiratory system than the effects of heavy smoke inhalation alone.

Thirteen years after 9/11, lung function declines related to toxic dust exposure persisted among World Trade Center first responders, with smokers and those with the greatest exposures having the largest pulmonary declines, researchers reported.

The latest follow-up of more than 10,500 New York City firefighters who were World Trade Center first responders or later responders confirms the lasting impact on lung function and the beneficial impact of smoking cessation on pulmonary decline trajectories, wrote Thomas Aldrich, MD, of Montefiore Medical Center and Albert Einstein College of Medicine in New York City, and colleagues in CHEST.

"We showed in this latest follow-up that smoking worsened lung function in this group of World Trade Center responders, which is not really a surprise," Aldrich told MedPage Today. "But we also showed that stopping smoking makes a major difference, and the earlier the better in terms of lung function."

Aldrich noted that more than 90% of World Trade Center responders developed acute coughs in the days and months following 9/11, and 50% or more developed persistent respiratory symptoms related to their exposure. About 1,000 firefighters who worked at "Ground Zero" have retired on respiratory disability, he said.

Most of these firefighters did not use respiratory protection devices, and Aldrich said this certainly contributed to their pulmonary declines. But he added that respiratory protection in a setting like 9/11, "is not as easy as it sounds."

"Firefighters have excellent protection when they fight ordinary fires -- self-contained breathing apparatus (SCBAs), which allow them to breathe fresh air from the tank while surrounded by toxic smoke and gases. But SCBAs last only 20 to 30 minutes at the breathing rates that occur during firefighting ... other forms of respiratory protection are, in general, either ineffective or too cumbersome and occlusive to be used during heavy labor."

The study included 10,641 World Trade Center-exposed New York City firefighters with pre-911 (baseline) forced expiratory volume in 1 second (FEV1) measurements and serial FEV1 measurements following exposure.

Previous follow-ups of the cohort at 1- and 7-years post exposure showed exposure-related FEV1 declines of 10% on average, with more than 10% of the cohort developing new obstructive airways disease.

"There was little recovery over the first six years," the researchers wrote. "Follow-up into the next decade allowed us to determine the longer-term exposure effects and the roles of cigarette-smoking and cessation on lung function trajectories."

From March 2000 to September 2014, the firefighters included in the study had a median of nine spirometry tests. Close to one in seven responders (15%) arrived at the World Trade Center on the morning of 9/11 and 65% were never smokers.

The analysis revealed that firefighters arriving on the morning of 9/11 continue to have significantly lower lung function, on average, than those arriving several days later (lesser-exposed firefighters) (P<0.05).

Those arriving the morning of 9/11 were more likely to have an FEV1 in the lower limit of normal (FEV1<LLN) compared with those arriving at the site between Sept. 11, 2001 and Sept. 24, 2001 (OR 1.70, P<0.01).

Also, current smokers were likely to have an FEV1<LLN compared with never-smokers (OR 2.06, P<0.01), former smokers who quit before 9/11 (OR 1.96, P<0.01), or those who quit between 9/11 and March 10, 2008 (OR 1.49, P<0.01).

"Particularly for firefighters and others in physically demanding occupations, falling below the lower limit of normal FEV1, and especially falling into the moderately severe impairment range (<70% predicted), can lead to serious lifestyle and employability changes," the researchers wrote. "For that reason, our findings that 20% of current smokers or those quitting after 2008 had abnormal lung function, and that the prevalence of abnormal lung function continued to rise throughout the study, help to demonstrate the magnitude of harm from smoking in this cohort."

The analysis is the longest study of lung function ever undertaken in rescue/recovery workers following a major environmental disaster. The availability of pre-exposure spirometry data and World Trade Center arrival times were also study strengths.

A limitation was the absence of data on pulmonary function in the first days following exposure, which hindered the ability to determine if early declines were more severe than the later testing suggested.

In an accompanying editorial, Lawrence C. Mohr, MD, ScD, of the University of South Carolina in Charleston, wrote that the magnitude of the persistent FEV1 decline in the firefighters who worked at "Ground Zero" has important implications, given that most studies of firefighter lung function following other exposures show acute injury followed by a return to normal.

"This finding suggests that the combined effects of the pulverized building materials and the chemical by-products of combustion and pyrolysis (high temperature decomposition) contained in the World Trade Center dust are significantly more toxic to the respiratory system than the effects of heavy smoke inhalation alone," he wrote.

Mohr added that the new finding showing smoking to have additive effect on FEV1 declines has important implications for firefighters.

"First, it suggests that smoking status should be carefully evaluated during the pre-employment medical evaluation of future firefighters, and evidence of smoking cessation should be provided by smokers prior to being hired," he wrote.

"Second, it provides strong evidence that the assessment of smoking status and aggressive smoking prevention or smoking cessation initiatives should be integral components of the preventive health care and health maintenance of all active duty firefighters. Finally, it demonstrates that the evaluation of smoking status and aggressive smoking prevention or smoking cessation initiatives should be integral components of all medical surveillance programs for firefighters who experience potentially toxic inhalational exposures during the response to a major disaster."

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

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